This invention relates to the transport of a multiplex of sampled signals from one location to another, and more particularly relates to such transport accomplished asynchronously.
For the transport of a multiplex of sampled signals from one location to another, there sometimes is a premium placed on maintaining fidelity for some of the sampled signals. Conventional processing of such sampled signals typically requires the original sampling clock (or a synchronously related version) in order to convert the digital data streams back into analog form. The conventional systems thus retain crucial sample time “information” contained in the sampling clock. The signal transport is sometimes complicated by the large amount of data per signal and large number of signals which must be multiplexed. As a result, efficiency is important in order to minimize the number of additional signals and/or clocks transported.
Experience has shown that distributing the original sampling clock signals available at a first location to a distant second location (the endpoint of the data transport) is prohibitively complex. In addition, there may be many such signals and clocks which require transport. Digital resampling of each data stream in the multiplex at the first location (onto a “suitable” clock signal, assuming a “suitable” clock signal is available) is unattractive because it results in a significant increase in word length prior to transport. Such a method is inefficient in that the amount of transported data is increased up to 50% by the resampling, if fidelity is strictly maintained. Time stamps can be imposed at the first location, but analysis shows that these are unable to provide the equivalent fidelity reconstruction available with the original sampling clock or with a resampling prior to transport, even with a significant change or improvement in the time-stamp implementation.
The present invention addresses the foregoing problems raised by conventional transport and provides alternative solutions.